The present invention relates to catalysts for the polymerization of olefins, and more particularly to ethylene polymers, and to a process for their preparation.
French Pat. No. 2,324,652 describes a process for the preparation of an olefin polymerization catalyst in which a titanium compound is brought into contact with the solid halogenation product obtained by reacting an organic acid halide with a magnesium alcoholate with the atomic ratio of halogen/Mg+Ti being greater than 2. The halogenation product contains a Lewis base, for example, the ester formed by reacting the organic acid halide with the magnesium alcoholate. The titanium compound is added during the reaction of the magnesium alcoholate with the organic acid halide and the atomic ratio of Ti/Mg is greater than 1.
It has now been discovered that if the atomic ratio of halogen/Mg+M is less than 1 during the reaction of an organic acid halide with a mixture of a magnesium alcoholate and a transition metal (M) alcoholate, with the ratio of M/Mg in the catalyst obtained being equal to at most 0.6 and without the ester formed by reacting the organic acid halide with the mixture of alcoholates in the catalyst formed, that a catalyst can be obtained having markedly improved activity.
Accordingly, an object of this invention is to provide a new and improved catalyst for the polymerization of olefins, and more particularly ethylene, having greater activity than known prior art catalysts.
Yet another object of this invention is to provide a process for the preparation of these catalysts.
Additional objects and advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.